Example reduction

As an introduction to the user, but also to check if IRDAP is installed correctly, a quick end-to-end example reduction can be performed. This demo uses a small portion of the H-band polarimetric data of the circumstellar disk of T Cha from ESO Program 096.C-0248(C). This data set was the first to be reduced with IRDAP’s correction method and is published in Pohl et al. (2017). It is also used in van Holstein et al. (2020) to exemplify the correction method.

To run the demo, change the current directory of the terminal to a directory of your choice and type:

irdap --demo

IRDAP then performs a complete data reduction and writes the resulting files to the terminal’s current directory.


An internet connection is required to run the demo, because 56.6 MB of raw data needs to be downloaded from the GitHub repository.

After running the demo, you can navigate to the reduced_pdi/no_star_pol_subtr subdirectory and open the files T_Cha_2016-02-20_Q_phi.fits and T_Cha_2016-02-20_U_phi.fits that show the final Q\(_\phi\)- and U\(_\phi\)-images. Opening these files with DS9, setting color to cool, scale to linear and the limits to -500 to 1500 and -300 to 150, respectively, you will see the following:


These images correspond to Figure 14 (left column) of van Holstein et al. (2020), but with lower signal-to-noise because for the demo the data of only 1 instead of 30 HWP cycles was used.

To start reducing your own data with IRDAP, continue to the usage instructions.